The present invention relates to an apparatus for the detection of voice signals in an input signal and in particular when such apparatus are used in alternation systems.
Such apparatus supply logic data, indicating the presence or absence of a word and can be used, for example, for controlling a switch in order to discriminate the voice signals with respect to the input signal.
Any truncation of the start or finish of voice activity is generally eliminated by adding a delay line which precedes the switch and delays the audiofrequency input signal.
It is known to produce alternating voice control apparatus of simple construction based on the comparison of the energy of the input signal and a fixed threshold. However, in the presence of noise, such apparatus are inadequate.
More efficient apparatus, essentially based on the spectral analysis of the signal are also known, but they suffer from a complicated construction.